Described herein is a method for determining the amount of interference in a received signal that comprises a wanted signal and a plurality of interfering signals. The capacitor supplies an electric current for the discharge lamp. The sensing circuit senses an environmental illumination intensity. More specifically, because each individual capacitor may be \u201cpre-tested\u201d and \u201caged\u201d, the likelihood that the final capacitor assembly will fail its performance test is minimal. The nozzle plate includes a substrate through which nozzles are formed; an ink-philic coating layer formed on an outer surface of the substrate and inner walls of the nozzles; and an ink-phobic coating layer selectively formed on the ink-philic coating layer disposed around the nozzles.